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[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index] [Xen-devel] [PATCH RFC v2 12/23] libxc/migration: specify postcopy live migration
From: Joshua Otto <jtotto@xxxxxxxxxxxx>
- allocate the new postcopy record type numbers
- augment the stream format specification to include these new types and
their role in the protocol
Signed-off-by: Joshua Otto <jtotto@xxxxxxxxxxxx>
---
docs/specs/libxc-migration-stream.pandoc | 175 +++++++++++++++++++++++++++++++
tools/libxc/xc_sr_common.c | 7 ++
tools/libxc/xc_sr_stream_format.h | 9 +-
3 files changed, 190 insertions(+), 1 deletion(-)
diff --git a/docs/specs/libxc-migration-stream.pandoc
b/docs/specs/libxc-migration-stream.pandoc
index 8342d88..9f08615 100644
--- a/docs/specs/libxc-migration-stream.pandoc
+++ b/docs/specs/libxc-migration-stream.pandoc
@@ -3,6 +3,7 @@
Andrew Cooper <<andrew.cooper3@xxxxxxxxxx>>
Wen Congyang <<wency@xxxxxxxxxxxxxx>>
Yang Hongyang <<hongyang.yang@xxxxxxxxxxxx>>
+ Joshua Otto <<jtotto@xxxxxxxxxxxx>>
% Revision 2
Introduction
@@ -231,6 +232,20 @@ type 0x00000000: END
0x0000000F: CHECKPOINT_DIRTY_PFN_LIST (Secondary -> Primary)
+ 0x00000010: POSTCOPY_BEGIN
+
+ 0x00000011: POSTCOPY_PFNS_BEGIN
+
+ 0x00000012: POSTCOPY_PFNS
+
+ 0x00000013: POSTCOPY_TRANSITION
+
+ 0x00000014: POSTCOPY_PAGE_DATA
+
+ 0x00000015: POSTCOPY_FAULT
+
+ 0x00000016: POSTCOPY_COMPLETE
+
0x00000010 - 0x7FFFFFFF: Reserved for future _mandatory_
records.
@@ -624,6 +639,142 @@ The count of pfns is: record->length/sizeof(uint64_t).
\clearpage
+POSTCOPY_BEGIN
+--------------
+
+This record must only appear in a truly _live_ migration stream, and is
+transmitted by the migration sender to signal to the destination that
+the migration will (as soon as possible) transition from the memory
+pre-copy phase to the post-copy phase, during which remaining unmigrated
+domain memory is paged over the network on-demand _after_ the guest has
+resumed.
+
+This record _must_ be followed immediately by the domain CPU context
+records (e.g. TSC_INFO, HVM_CONTEXT and HVM_PARAMS for HVM domains).
+This is for practical reasons: in the HVM case, the PAGING_RING_PFN
+parameter must be known at the destination before preparation for paging
+can begin.
+
+This record contains no fields; its body_length is 0.
+
+\clearpage
+
+POSTCOPY_PFNS_BEGIN
+-------------------
+
+During the initiation sequence of a postcopy live migration, this record
+immediately follows the final domain CPU context record and indicates
+the beginning of a sequence of 0 or more POSTCOPY_PFNS records. The
+destination uses this record as a cue to prepare for postcopy paging.
+
+This record contains no fields; its body_length is 0.
+
+\clearpage
+
+POSTCOPY_PFNS
+-------------
+
+Each POSTCOPY_PFNS record contains an unordered list of 'postcopy PFNS'
+- i.e. pfns that are dirty at the sender and require migration during
+the postcopy phase. The structure of the record is identical that of
+the PAGE_DATA record type, but omitting any actual trailing page
+contents.
+
+ 0 1 2 3 4 5 6 7 octet
+ +-----------------------+-------------------------+
+ | count (C) | (reserved) |
+ +-----------------------+-------------------------+
+ | pfn[0] |
+ +-------------------------------------------------+
+ ...
+ +-------------------------------------------------+
+ | pfn[C-1] |
+ +-------------------------------------------------+
+
+\clearpage
+
+POSTCOPY_TRANSITION
+-------------------
+
+This record is transmitted by a postcopy live migration sender after the
+final POSTCOPY_PFNS record, and indicates that the embedded libxc stream
+will be interrupted by content in the higher-layer stream necessary to
+permit resumption of the domain at the destination, and further than
+when the higher-layer content is complete the domain should be resumed
+in postcopy mode at the destination.
+
+This record contains no fields; its body_length is 0.
+
+\clearpage
+
+POSTCOPY_PAGE_DATA
+------------------
+
+This record is identical in meaning and format to the PAGE_DATA record
+type, and is transmitted during live migration by the sender during the
+postcopy phase to transfer batches of outstanding domain memory.
+
+ 0 1 2 3 4 5 6 7 octet
+ +-----------------------+-------------------------+
+ | count (C) | (reserved) |
+ +-----------------------+-------------------------+
+ | pfn[0] |
+ +-------------------------------------------------+
+ ...
+ +-------------------------------------------------+
+ | pfn[C-1] |
+ +-------------------------------------------------+
+ | page_data[0]... |
+ ...
+ +-------------------------------------------------+
+ | page_data[C-1]... |
+ ...
+ +-------------------------------------------------+
+
+It is an error for an XTAB, BROKEN or XALLOC pfn to be transmitted in a
+record of this type, so all pfns must be accompanied by backing data.
+It is an error for a pfn not previously included in a POSTCOPY_PFNS
+record to be included in a record of this type.
+
+\clearpage
+
+POSTCOPY_FAULT
+--------------
+
+A POSTCOPY_FAULT record is transmitted by a postcopy live migration
+_destination_ to communicate an urgent need for a batch of pfns. It is
+identical in format to the POSTCOPY_PFNS record type, _except_ that the
+type of each page is not encoded in the transmitted pfns.
+
+ 0 1 2 3 4 5 6 7 octet
+ +-----------------------+-------------------------+
+ | count (C) | (reserved) |
+ +-----------------------+-------------------------+
+ | pfn[0] |
+ +-------------------------------------------------+
+ ...
+ +-------------------------------------------------+
+ | pfn[C-1] |
+ +-------------------------------------------------+
+
+\clearpage
+
+POSTCOPY_COMPLETE
+-----------------
+
+A postcopy live migration _destination_ transmits a POSTCOPY_COMPLETE
+record when the postcopy phase of a migration is complete, if one was
+entered.
+
+This record contains no fields; its body_length is 0.
+
+In addition to reporting the phase completion to the sender, this record
+also enables the migration sender to flush its receive stream of
+in-flight POSTCOPY_FAULT records before handing control of the stream
+back to a higher layer.
+
+\clearpage
+
Layout
======
@@ -676,6 +827,30 @@ A typical save record for an x86 HVM guest image would
look like:
5. HVM\_CONTEXT
6. HVM\_PARAMS
+x86 HVM Postcopy Live Migration
+-------------------------------
+
+The bi-directional migration stream for postcopy live migration of an
+x86 HVM guest image would look like:
+
+ 1. Image header
+ 2. Domain header
+ 3. Many (or few!) PAGE\_DATA records
+ 4. POSTCOPY\_BEGIN
+ 5. TSC\_INFO
+ 6. HVM\_CONTEXT
+ 7. HVM\_PARAMS
+ 8. POSTCOPY\_PFNS\_BEGIN
+ 9. Many POSTCOPY\_PFNS records
+10. POSTCOPY\_TRANSITION
+... higher layer stream content ...
+11. Many POSTCOPY\_PAGE\_DATA records
+
+During 11, the destination would reply with (hopefully not too) many
+POSTCOPY\_FAULT records.
+
+After 11, the destination would transmit a final POSTCOPY\_COMPLETE.
+
Legacy Images (x86 only)
========================
diff --git a/tools/libxc/xc_sr_common.c b/tools/libxc/xc_sr_common.c
index f443974..090b5fd 100644
--- a/tools/libxc/xc_sr_common.c
+++ b/tools/libxc/xc_sr_common.c
@@ -38,6 +38,13 @@ static const char *mandatory_rec_types[] =
[REC_TYPE_VERIFY] = "Verify",
[REC_TYPE_CHECKPOINT] = "Checkpoint",
[REC_TYPE_CHECKPOINT_DIRTY_PFN_LIST] = "Checkpoint dirty pfn list",
+ [REC_TYPE_POSTCOPY_BEGIN] = "Postcopy begin",
+ [REC_TYPE_POSTCOPY_PFNS_BEGIN] = "Postcopy pfns begin",
+ [REC_TYPE_POSTCOPY_PFNS] = "Postcopy pfns",
+ [REC_TYPE_POSTCOPY_TRANSITION] = "Postcopy transition",
+ [REC_TYPE_POSTCOPY_PAGE_DATA] = "Postcopy page data",
+ [REC_TYPE_POSTCOPY_FAULT] = "Postcopy fault",
+ [REC_TYPE_POSTCOPY_COMPLETE] = "Postcopy complete",
};
const char *rec_type_to_str(uint32_t type)
diff --git a/tools/libxc/xc_sr_stream_format.h
b/tools/libxc/xc_sr_stream_format.h
index 32400b2..d16d0c7 100644
--- a/tools/libxc/xc_sr_stream_format.h
+++ b/tools/libxc/xc_sr_stream_format.h
@@ -76,10 +76,17 @@ struct xc_sr_rhdr
#define REC_TYPE_VERIFY 0x0000000dU
#define REC_TYPE_CHECKPOINT 0x0000000eU
#define REC_TYPE_CHECKPOINT_DIRTY_PFN_LIST 0x0000000fU
+#define REC_TYPE_POSTCOPY_BEGIN 0x00000010U
+#define REC_TYPE_POSTCOPY_PFNS_BEGIN 0x00000011U
+#define REC_TYPE_POSTCOPY_PFNS 0x00000012U
+#define REC_TYPE_POSTCOPY_TRANSITION 0x00000013U
+#define REC_TYPE_POSTCOPY_PAGE_DATA 0x00000014U
+#define REC_TYPE_POSTCOPY_FAULT 0x00000015U
+#define REC_TYPE_POSTCOPY_COMPLETE 0x00000016U
#define REC_TYPE_OPTIONAL 0x80000000U
-/* PAGE_DATA */
+/* PAGE_DATA/POSTCOPY_PFNS/POSTCOPY_PAGE_DATA/POSTCOPY_FAULT */
struct xc_sr_rec_pages_header
{
uint32_t count;
--
2.7.4
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